1. Field of the Invention
The present invention relates to a mobile communication relay device that users can easily carry, and in particular, relates to a device capable of connection to a plurality of external networks in a configuration that relays communication between an internal network and an external network.
2. Description of the Related Art
Heretofore, a communication relay device known as a wireless LAN router is in widespread use as a device enabling a plurality of terminal devices to connect to external networks such as the Internet in residential or corporate settings. The device configures a LAN (Local Area Network) that is an internal network between the device and a terminal device, and is loaded with a function for routing communication from a communication terminal to an external network, a Dynamic Host Configuration Protocol (DHCP) server function for allocating an Internet Protocol (IP) address for the communication terminal, a Network Address Translation (NAT) function for performing address conversion, a Domain Name System (DNS) server function for converting a domain name and an IP address (DNS forward function), for example.
On the other hand, with communication environments on the street (e.g., wireless hotspots), various wireless access systems such as a mobile telephone, a wireless LAN, and a Personal Handy-phone System (PHS) are widespread, and a wireless Metropolitan Area Network (MAN) service such as WiMax is being introduced.
While these various wireless access systems are being offered, beyond the configuration enabling a connection to a wireless LAN in residential or corporate setting that is not sufficient, there is a growing demand for sharing an external network connection by using a plurality of communication terminals even when the user is away from his/her usual place. There is also a growing demand for separating various connection machines and connection processing depending on each wireless access system from a communication terminal main body.
One product presently available is “Wireless Gate Home Antenna for emobile” from TripletGate Inc. of Tokyo, Japan which is a device that relays a connection to the Internet by High-Speed Download Packet Access (HSDPA) and provides an external connection for a terminal by wireless LAN (referenced in Non-Patent Document 1).
This device is capable of Internet connection to a plurality of terminals simply when the device is installed, even in locations where wired networks cannot be utilized.
However, this device can only be connected to a single wireless operator using HSDPA. Therefore, in addition to the inability to be used outside of the HSDPA area, even an area offering a more suitable wireless access system cannot be selected.
On the other hand, even by using a technique already available including a method in which a communication adapter to handle a plurality of wireless access systems is installed in a well-known personal computer so that the user is allowed to switch a connection destination by him/herself is employed, various types of external networks can be selectively used.
However, it is often not conveniently portable, and the effort to understand and manually switch the communication areas, and the like, is troublesome.
A known technique is disclosed in Japanese Patent Laid-Open No. 2003-283536 (Patent Document 1), which teaches a mobile router device including a first wireless interface for connecting to a first network and a second wireless interface for connecting to a second network different from the first network. The device is configured to include an address assignment portion for assigning an IP address that a user personally retains in advance for a plurality of communication terminals connected to the second wireless interface, and a communication controller for connecting the second wireless interface and the first wireless interface by utilizing the IP address assigned by the address assignment portion so as to perform packet transmission and reception between the first network and the communication terminal.
The above-described device is similar to that offered by TripletGate described above, and does not functionally differ from a well-known stationery wireless LAN router. Therefore, there is not provided in the art a technique for selectively using available wireless access systems offered by various wireless operators according to a location and an application or use.
Patent Document 1: Japanese Patent Laid-Open No. 2003-283536
Non-Patent Document 1: Internet URL, http://www.tripletgate.com/wirelessgate/news/homeantenna.pdf (searched on Feb. 5, 2009).